Field Symbols基本使用教程

1、定义Field Symbols

1. TYPES: tt_mara TYPE STANDARD TABLE OF mara.
   
2. DATA:  t_mara TYPE tt_mara.
   
3. 
   
4. FIELD-SYMBOLS: <lfs_mara> LIKE LINE OF t_mara.
   
5. 
   
6. " Field symbol without type
   
7. FIELD-SYMBOLS:
   
8.   <lfs_any_tab> TYPE ANY TABLE,
   
9.   <lfs_any> TYPE any.

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2、APPEND and INSERT操作

1. * Append line
   
2. APPEND INITIAL LINE TO t_mara ASSIGNING <lfs_mara>.
   
3. <lfs_mara>-matnr = 'sapclub'.
   
4. 
   
5. * insert table
   
6. INSERT INITIAL LINE INTO t_mara ASSIGNING <lfs_mara> INDEX 2.
   
7. <lfs_mara>-matnr = 'ABCDEF'.

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3、访问内表行记录

1. * Read table
   
2. READ TABLE t_mara ASSIGNING <lfs_mara> WITH KEY matnr = 'sapclub'.
   
3. IF sy-subrc EQ 0.
   
4.   WRITE:/ <lfs_mara>-matnr.
   
5. ENDIF.
   
6. 
   
7. * Access via Loop
   
8. LOOP AT t_mara ASSIGNING <lfs_mara>.
   
9.   WRITE:/ <lfs_mara>-matnr.
   
10. ENDLOOP.

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4、Modify 内表行记录

1. * READ and MODIFY
   
2. READ TABLE t_mara ASSIGNING <lfs_mara> WITH KEY matnr = 'sapclub'.
   
3. IF sy-subrc EQ 0.
   
4.   <lfs_mara>-ersda = sy-datum.
   
5. ENDIF.
   
6. 
   
7. * LOOP and MODIFY
   
8. LOOP AT t_mara ASSIGNING <lfs_mara>.
   
9.   <lfs_mara>-ersda = sy-datum + 1.
   
10. ENDLOOP.

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5、检查Field Symbols是否被分配ASSIGNED

1. * Check if Field-Symbol is assigned
   
2. IF <lfs_mara> IS ASSIGNED.
   
3.   WRITE:/ 'Assigned'.
   
4. ELSE.
   
5.   WRITE:/ 'Unassigned'.
   
6. ENDIF.

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注意不能使用sy-subrc = 0来判断是否被分配

6、解除Field Symbols参考关系

1. "remvoe the reference
   
2. UNASSIGN <lfs_mara>.

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UNASSIGN：初始化<FS>字段符号，执行后字段符号将不再引用内存区域
CLEAR：与UNASSIGN不同的是，作用是初始化它所指向的内存区域，而不是解除分配